I fell into writing about health shortly after grad school, where I realized I didn't want to work in a lab for the rest of my life! My areas of interest are the brain and behavior, as well as what influences the decisions we make about our health, and how the media helps and hinders people's understanding of health issues. As an undergraduate, I studied English Literature and Biopsychology at Vassar College, and got my PhD in Biopsychology and Behavioral Neuroscience at CUNY's Graduate Center in New York City, where I grew up and live now. My day job is as Associate Editor with the health website, TheDoctorWillSeeYouNow.com. My work has appeared in several other publications, including TheAtlantic.com and YogaGlo.com, and I'm particularly excited to join the Forbes health team. Email me at alicegwalton [at] gmail [dot] com .

The Neuroscience of Pot: Researchers Explain Why Marijuana May Bring Serenity Or Psychosis

According to the experts, and to people who use it, pot can have widely disparate effects on people’s behavior, depending on…well, that part is still a bit unclear. Marijuana has been shown to have both anxiolytic (anti-anxiety) effects and to induce anxiety and psychosis in certain people. In schizophrenics, it can increase symptoms, and in healthy people it can increase the risk of schizophrenia. Now, new study shows that the two active ingredients in pot, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) may have quite opposite effects on the brain – and behavior – and could explain why pot’s effects can be unpredictable.

In the new study, the researchers had 15 men who were relatively unseasoned pot users take capsules containing THC, CBD, and flour (placebo) on each of three occasions. The participants then took simple computer tests in which arrows, pointing either left or right, flashed on the screen; the men had to respond based on their direction. Occasionally, an “oddball” arrow was thrown in to the sequence, which was at a 23-degree angle.

This setup allowed the researchers to compare the men’s reactions to usual vs. oddball stimuli, and to see how the various chemicals affected it. How people react to mundane environmental cues vs. the unexpected ones is thought to be linked to mental health, and therefore, to disorders. So, the men’s reaction times were measured, and their brains were scanned with fMRI to see what was going on neurologically. Their psychotic symptoms were also compared across conditions.

The men who had taken THC had more psychotic symptoms like altered thinking (paranoid and delusional thoughts) than men who’d taken either CBD or placebo.

The THC also had a greater effect on reaction time to the standard, rather than the oddball, conditions. This suggests that THC could change what people see as important environmental stimuli (more on this later). Men who had taken the THC also had less activation in the caudate nucleus: and the less activity in the area, the more marked the men’s psychotic symptoms and affected their reaction times. Alterations in the activity in the striatum and prefrontal cortex also suggested a possible mechanism for the increase of psychotic symptoms.

Taking CBD, however, had the opposite effect of THC. It tended to speed up response time to the oddball stimuli, compared to the standard ones, which suggests that it works with our natural tendency to react to unexpected stimuli, rather than against it. And the brain regions that were activated after CBD ingestion were largely counter to those activated with THC. Previous research has suggested that CBD has antipsychotic effects, and this seems to be supported by the current study.

So what’s the relationship between response to arrows on a screen and psychotic symptoms? Normally, people tend to react to out-of-the-ordinary stimuli over the usual ones. In this study, however, people on THC had boosted responses to the mundane stimuli, and were less responsive to the unexpected ones. In the real world, if one has problems ignoring ordinary stimuli in the environment – and even has a ramped-up or atypical response to them – this could creep into the territory of hallucination. Earlier studies have found links between chronic marijuana use and an increased risk for developing psychotic symptoms. Of course, it’s hard to tell whether marijuana use leads to mental health problems or already having mental health problems leads to increased marijuana use, but this and other studies suggest that it’s more likely the former case.

On the other hand, CBD seems to counter the effect of THC, and could (possibly) be used as an antipsychotic. The team’s earlier work actually showed that pretreatment with CBD can block the psychotic effects of THC administration.

The problem is that most people don’t ingest CBD or THC capsules in real life. They smoke pot, which includes both chemicals. Therefore, the study doesn’t quite explain why taking in both chemicals in at the same time would have different effects in different people (or different effects in the same person on different occasions). For example, why some people are more susceptible to the negative effects of the drug than others is still unclear, but it may be due to the patterns of the different cannabidiol receptors in the brain or other differences that have yet to be determined.

The study does help explain why synthetic marijuana has been linked to more adverse effects than natural cannabis. Synthetic forms of the drug, like K2, which have been associated with more hallucinations, agitation, and ER visits, are made largely of chemicals that are thought to mimic THC.

Future studies will have to look into some of these remaining questions, but this study makes a good stab at explaining why marijuana can lead to such different experiences in people who use it.

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Thanks for this. I know many young people who started smoking pot at 12 or 13 and continued smoking pot on a daily basis until they were in their early 20s when the rapt attention to unimportant stuff starts to eat away at your ability to function in the ‘real world.’

I like pot-heads. Always have. There’s a certain “go with the flow-ness” of them that appears to me to be a character trait of people who are attracted to the drug in the first place. When these young people stop taking the drug, the good effect – not getting one’s panties all in a bunch over little things – seems to persist, suggesting that there’s a type of person who is attracted to the drug – that character (personality) moves the person toward the drug rather than the drug creating a certain type of person.

Those people I’ve know who are Type-A achievers, tend to have more bad effects of the panic variety in response to marijuana, after which they avoid it and, if they’re looking for a soporific, move toward alcohol and away from marijuana.

I say all this anecdotally rather than based on research because I’ve worked with alcoholics and drug addicts since I first started doing peer crisis and drug/alcohol abuse counseling when I was 19 years of age.

For the record, I haven’t personally inhaled for 18 years, but I can attest to the drug’s anti-anxiety effect as far better than alcohol because it simply breaks the connection between the user and anything of substance that might upset the user – like tomorrow’s physics exam. Hence the reason for either refusing to legalize this drug or to make certain there are as many rehab programs as there are Starbucks locations.

There has been thousands of reports to poison control over the past few years for herbal incense and other artificial cannabanoids. With legal restrictions what they are now our youth has turned to “Spice” which is becoming more dangerous than drugs such as cocaine and heroin. With all of the benefits that marijuana possesses, it is hard to understand why they are waiting to pass legislation.

Your Sativa strains are much more likely to produce anxiety disorders, your Indica strains are more likely to relax and sedate. Hydrids are somewhere in between with a combination of both of the two major strains, but either being sativa dominate or indica dominate. CBD has more of the anti-pain, anti-inflammatory properties; while THC has psycho-active components…the head-high.

There is no “big secret” about marijuana. The reason that Big Pharma keeps trying (and failing) to create a “pill” from it is that it’s a complex plant with dozens or hundreds of cannabinoids that work together. The particular strain, growing and curing method, and even how it is consumed changes the effects. Even taking too high of a dosage can take you past merely “high” and bring out the effects of the other cannabinoids. That’s why I advise medical marijuana patients to find a strain that works for them, stick to it, and take the minimum they need for their symptoms.

And by the way…Canna Caps are indeed very popular among serious patients.